The conventional metal-vapor pulsed laser uses only two electrodes, i.e., a cathode and an anode, to produce high-output pulsed discharge directly.
However, in order to obtain further improved output and efficiency with this conventional structure using only two such electrodes, it has been necessary to improve the pulsed discharge characteristics by making the equipment such as the laser tube itself bigger, arranging expensive circuit elements in multi-stages, or adding a magnetic compression circuit using a saturable reactor or the like to the discharging circuit. As a result, such discharge circuits ate very complex. Hence, it is not easy to achieve a higher output and a higher efficiency. Additionally, the cost is increased greatly. In this way, various problems have taken place.
Furthermore, the cathode is impacted by ions from a discharging plasma, because an electric discharge is directly produced between the cathode and anode. This accelerates deterioration of the cathode. Consequently, the life of the cathode is short.